Fluid pressure control system



Nov. 4, 1958 L. D. ETHlNGToN ET AL 2,858,803

FLUID PRESSURE CONTROL SYSTEM Filed DeC. 6, 1956 2 Sheets-Sheet l Nov. 4, 1958 L. D. ETHlNGToN ET AL FLUID PRESSURE SONTROE SYSTEM 2 Sheets-Sheet 2 Filed" Deo. 6, 1956.

' including a tractor-mounted control valve and a United States Patent O and Lewis K. Davis, Waterloo, Iowa, assignors, by mesne assignments, to Deere & Company, a corporation .of Delaware Application December 6, 1956, SerialNo. 626,708 1s claims. (c1. 121-38) This invention relates to a huid pressure control system and more particularly to improved valve mechanism for obtaining-selective control.

The invention finds particular utility in a background organization such as that disclosed in the U. S. Patents to Fletcher 2,615,430, 2,546,831 and Re. 23,537. As depicted primarily in Fletcher 2,615,430, an agricultural tractor is equipped with a hydraulic power control system remotely located cylinder mounted on an implement, for example, connected to the tractor. Without more, manipulation of the control valve will extend and retract the cylinder but, as an adjunct to the ilexibility of the system, means is provided for limiting the stroke of the cylinder in at least one direction irrespective of. whether the control valve is held open for a longer interval. The stop means operates fundamentally on the basis of the principle that fluid tiovv from the cylinder is blocked or reduced to such an extent as to cause return of the control valve to its neutral position as a result of the abnormal rise in pressure.v In the system there disclosed, the first action of the stop Imeans is one to reduce the iluid flow for incurring return of the control valve to its neutral position, but the means whereby the fluid flow is restricted or reduced rather than being blocked completely affords a restricted orilicegthrough which overtravel beyond the stop position may be had by forcibly opening the control valve again.

The present invention pertains to a modification of the foregoing structure by the superimposition of selector means for cuttingout the provision of overtravel of the stop when desired. Itis va significant feature of the present invention 'to provide a structure which may be substituted for that of the prior patents for effecting the conversion .of existing remote cylinders..

Specifically, it is an object of the invention to utilize a dual-valve arrangement in which the valves are normally -movable respectively through different distances and to modify this arrangement so as to shorten the distance through which one of the valves is movable whereby sooner to achieve the ultimate-positionof said one valve. The invention improves theformer structure =by the provisiony of means enabling overtravel at high speed rather than vat slow speed', the provisionof improved drive means between the two valves and between at least one `of thefvalves and the control member that causes movement of the valves; and such' other features and objects as will appear in greater detail from the ensuing speciiication and accompanying sheets of drawings, the several figures of which are described immediately below.

Fig. l is a longitudinal half section of a cylinder and piston assembly, showing the valve mechanism just before it is actuated. 1

Fig. 2 is a similar View showing the valve mechanism in an intermediate stage.

Fig. 3 is a similar Yview showing actuation of the selector means to reposition the internal valve.

Fig. '4 is a similar sectional view showing the relationgatented Nov. 4, 1958 2 ship ofthe inner and outer valves at the stroke-lirniting position thereof.

The basic arrangement of the disclosure of the aboveidentified patent to Fletcher 2,615,430 may be taken as representative of the background in which the present invention finds particular utility; although, obviously, the invention is not thus limited. Likewise, such expressions as f1-ont, rear, etc. are used lhere as well as in the claims as terms of convenience and not of' limitation.

With the foregoing in mind,l the basic element in which the valve structure is mounted is a first element or cylinder 10 formed with a chamber 12 to and from which uid is conducted by means of a passage 14, it being understood that the passage 14 is connected to a remote control valve such as that identified in the abovementioned patent. A piston 16 represents a secondelement comprising an internal part movable back and forth in the cylinder chamber 12 and having a piston rod 18 representing an external part which of course reflects movement of the piston 16. The free end of the piston rod has a clevis 20 thereon which cooperates with a clevis 22 at the opposite end of the cylinder 10 for lmounting the cylinder-piston assembly between a pair of parts capable of relative adjustment by extension d and retraction of the cylinder.

it will be understood that the cylinder can be of the two-wayA type in which iluid supplied through the passage 14 and a continuation passage portion 24 extends the cylinder-piston assembly by forcing the piston 16 to the right, and that another passage, not shown, is capacitated to introduce uid under pressure at the right hand end of thel piston, as via a passage portion 26, to contract the assembly by forcing the piston 16 to the left. As an incident to extension of the cylinder, iluid to the right of the piston will be expelled through the passage 26 and retraction of the cylinder will result in exhaust of fluid from the left hand side of the cylinder through the passage 24-14.

The control valve mechanism, identified generally by the numeral 28, is instrumental in controlling the oW of lluid from the chamber lI2 through the passage 24-14; although, the valve mechanism will, of course, open to admit fluid to the chamber 12 from the passage 14.

'A supporting portion 30, integral with or otherwise connected to the cylinder 10, anords a fore-and-aft valve bore 32 which intersects the passage 14--24V at a valve seat 34. The valve bore 32 vcarries therein for advance toward the seat 34 a iirst valve 36 having a forward head 38 and a rear tubular part 40. The valve 36 has a normal rearwardly stopped position (Fig. l) which is effected by stop'means including a washer 42' at a necked-down portion 44 of a rearward enlarged extension chamber 46 of thel valve bore 32; and biasing means in the form of a coiled compression spring '48 operates between the front end of the Valve-housing chamber 46 and a shoulder 50 on the valve 36 to urge the valve rearwardly to the stopped position just identified. A sleeve 52 abuts the forward portion of the chamber 46 and also abuts the washer 42 to prevent forward displacement of the washer. Y

When the valve 36 is advanced from its normal rearwardly stopped position as shown in Fig. l, its head 38 seats on the passage-control seat 34 and would block Huid flow through the passage 14--24 except for the provision in the head of orice means comprising a pair of restrictive holes or ports 54 and 56 which, as shown in Fig. 2, for example, enable ow of fluid at a reduced rate through the passage 14--24. The reduction in rate is suiiicient, however, to create an abnormal pressure rise in the control system suflicient to actuate the main control valve (not shown) as in lthe Fletcher patents identified above. Also, the fact that a reduced flow is available enables a remanipulation of the control valve to exhaust fluid at said reduced rate so that the piston 16 can have overtravel to the left of the position shown in Fig. 2, the amount of which overtravel is determined by the time of closing of an internal or second valve 58.

In the preferred construction illustrated, the tubular rear part 40 ofthe large or outer valve 36 coaxially carries the inner valve 58 which itself is tubular to have a rear tubular part 60 and a closed front end or head 62 which is adapted to seat, upon advance of the valve 58, on arear or inner seat 64 formed interiorly of the valve 36 in controlling relationship to the orifice means provided by the restrictive openings 54 and 56. In short, when the valve 58 seats on the seat 64, the orifice means is blocked and the aforesaid reduced flow of fluid is stopped completely.

It will be apparent from the foregoing that if the valve 3 6 ,is made responsive to the position of the piston 16 and if the orifice ports 54 and 56 are eliminated, the valve 36 when closed would provide a positive stop limiting the stroke of the piston and having no provision for overtravelr, such as is available by incorporating the ports 54 and `56 and the second valve 58. However, experience with the former Fletcher designs has evidenced the broad desirability of the provision for a limited stop supplemented by provision for overtravel. On the other hand, further experience has shown that in enough instances to warrant utilization of the present invention there is need for a system in which the provision for overtravel can be cut in or cut out at will, and this is here accomplished in a manner to be presently described.

A coaxial continuation of the valve mechanism housing 46, here comprising a bore 66, is equipped with a combination seal and bushing 68 which carries a foreand-aft movable control member or rod 70 which has at its free or outerrear end one-way means 72 engageable by a selectively adjustable stop 74 movable with the piston rod 18 as an indication of the position of the piston 16 and settable to determine the amount of travel of the piston 16 to the left in the cylinder chamber 12. For -present purposes, the means 72 need not be considered as anything more than a lugafxed to the free end of the rod 70 as by a cross pin 76, and the member 74 may be mounted on the piston rod 18 in a manner such as that illustrated in the Fletcher Patent 2,615,430, mentioned above.

The control member or rod 70 is urged rearwardly to va normally stopped rear position by biasing means comprising a coiled compression spring 78 which encircles that portion of the rod 70 within the neckedfdown portion 44 and bore extension 66, one end of the spring seating against the stop washer ,42 and at the other end seating against a stop afforded by a ring and washer assembly 80 on the rod 70. Rearward extension of the rod 70 under action of the biasing means 78 beyond the position shown in Fig. l is prevented by a forward stop 82 which engages the washer 42 from in front. From lthe description thus far, it will be seen that the lug or one- .way means 72 on the free end of the rod 70 depends into the path of the adjustable but xed stop 74 on the piston rod 18, so that as the piston 16 and rod `18 move to the left, the stop 74 ultimately engages the lug 72 from behind and moves the control member 70 forwardly against the action of its biasing spring 78. As will be brought out below, this action of the control member 70 is utilized to effectuate either sequential or simultaneous closing of the valves 36 and 58.

v, For this purpose, the Yforward end portion of the convtrol member 70 extends into the rear tubular part 60 of the inner valve 58 to afford a lost-motion connection 84 which includes a detent ball 86 and front and rear stops afforded by fore-and-aft spaced apart shoulders 88 and 90, respectively, on the forward portion of the rod 70. The ball 86 is retained in an aperture 92 in the wallof the tubular part 60 of the inner valve S8 and since the ball is retained fore-and-aft between the shoulders 88 and 90 the lost-motion connection effects drive means between the rod 70 and the-valve 58. The lost-motion connection is biased by a compression spring 94 contained within the valve 58 and acting to take up the lost-motion by normally urging the valve 58 forwardly relative to the rod 70 so that the detent is engaged with the front shoulder 88, on the back of which is formed 'a front cam surface 96 which, together with a rear cam surface 98, cooperates with the detent 86 to effect a drive connection with the outer or larger valve 36 by means of an abutment or annular shoulder 100 on the inner tubular wall of the latter. Since the biasing spring 94 within the lvalve 58 normally urges the valve 58 forwardly, it seats the detent ball 86 on the front cam 96 and therefore urges the ball radially outwardly into engagement with the annular shoulder 100 on the valve 36, thus effecting the drive connection just referred to. If the valve 58 is moved rearwardly relative to the control rod 70, compressing the spring 94, the detent 86 will drop down onto the rear cam surface 98 and thus will retract or disengage from the abutment afforded by the lannular shoulder 100. In the preferred construction illustrated, the front and rear shoulders on the front end of the control rod 70 are annular, as are the front and rear cams 96 and 98; although, the same results could be otherwise accomplished.

The rear end of the cylinder 10 carries a support in the form of a bracket 102 which mounts selector means 104 operative to establish for the valve 58 a second rear position ahead of the rear position it normally occupies when the rod return spring 78 returns the rod 70 to its maximum rear position. The means 104 is here shown as comprising a set screw 106 and lock nut 108 and is operative to be'extended into or retracted from the path of the one-way lug 72 on the controly rod 70; although, other means of accomplishing the same result will readily suggest themselves. Figs. l and 2 show the retracted position of the means 104 and Figs. 3 and 4 show the extended position of the means.

A vent hole 110 (Figs. l and 2)l in the forward part of the large valve 36v prevents entrapment of fluid between the two valves 36 and 58.

Operation-Stop and overtravel In this phase of operation, the conditions are that the piston rod stop 74 is xed to the piston rod in a selected position, the stop means 104 is retracted and the cylinder piston assembly is extended as shown in Fig. 1 so that the rod 70 is fully extended to its maximum limit and the valves 36 and 58 are open or unseated.

As the main control valve (not shown) is manipulated to supply uid under pressure through thepassage 26 to the right hand side of the piston 16 and to exhaust uid fromthe left hand side of the piston via the passage 24-14 past the open valve seat 34, the piston 16 and piston rod 18 move to the left, the piston rod stop 74 approaching the lug 72 on the control rod 70. As engagement is effected between the stop 74 and the lug 72, the rod 70 is advanced to the left (Fig. 2). The biasing action 94 which affects the lost-motion connection 84 is extended to retain the ball 86 on the front cam 96 and therefore in engagement with the valve 36 via the annular abutment shoulder 100. Since the ball 86 is retained in the aperture 92 in the valve 58, the connection between the Control member 70 and the valve 58 is permanent. Hence,` as the piston rod stop 74 picks up the control rod 70, the now activated drive connection 84- 86-100 causes advance of thevalves 36 and 58 in unison until the head 38 on the valve 36 seats at the valve seat 34 to block the passage 24 except for the reduced fluid flow permissible through the orifice means 56-54. As stated above, the reduction inflow is sucient to cause in the hydraulic system an abnormal rise in pressure elective to return the main control valve to neutral. ,Consequently, the piston 16 is automatically stopped in the porarily engage the rod lug 72 either earlier or "control rod 70.

As is recognized by those familiar with the general problem involved here, the purpose of the automatic stop is to permit a repetition of the retracting stroke of the cylinder piston assembly throughout successive operations. Asis also recognized, there are instances in which exact repetition is not required and it is therefore desirable or necessary to modify the stroke by permitting overtravel beyond the stopped position. In the present case, overtravel will involve further retraction of the cylinder piston assemblyV to the dotted-line position of Fig. 2. Overtravel is available with the valves 36 and 58 in Fig. 2 position by further manipulation of the main control valve sorthat additional fluid under pressure is supplied to the right side of the piston via the passage 26. Although the uid at the left hand side of the piston will exhaust slowly through the orifice means 56--54, overtravel is necessarily accomplished. This overtavel will of course entail further advance of the control rod 70 relative to the stopped valve 36 and since the detent ball 86 is engaged between the stopped valve 3 6 and-the temstopped valve 58, the spring 94 within the valve 58 will yield upon advance of the control rod so that the rear or reduced cam surface 98 is presented beneath the ball 86, thereby allowing the ball to retract from its engagement with the abutment shoulder 100 on the valve 36. This, then, deactivates the drive connection between the two valves and the valve 36 is free to snap back to its normal rearwardly stopped position under action of its biasing means 48.

Since the valve 36 returns toward its normal position it accordingly becomes unseated at 34-38 and therefore removes the restriction setup by the orifice means 54-56 and consequently overtravel may be obtained at the same speed as the original portion of the stroke before the valve 36 was previously seated. At the same time, since the drive connection between the two valves is now disconnected, because the valve 58 is now ahead of the valve 36, the valve 58 will ultimately pick up the valve 36 via engagement of the head 62 of the valve 58 with the inner seat 64 on the valve 36 and both valves will move simultaneously until the valve 36 is again seated at 34-38. Since the inner valve 58 is seated at 62-64 the orifice means 54-56 is blocked and fluid ow is cut olf forthwith, thereby again incurring pressure rise in the system to automatically return the control valve to neutral. In systems lacking the automatic return of control valve to neutral, the operator will become aware of the stop condition either by chattering of the overload relief valve or simply by noting that the cylinder-piston assembly is at the end of its predetermined retraction stroke.

When it is desired to reextend the cylinder-piston assembly, iluid under pressure is admitted via the inlet 14 and this fluid enters the oriiice 54 at a rate sufficient to force the valve 58, which is seated at 62-64, back against its lost-motion biasing spring 94, thereby uncovering the oriice 56 which is Aat present in register with the passage 24. Therefore, fluid ow to the left hand side of the piston 16 is available at a sufiicient rate lto cause the piston 16 to move to the right. As this occurs, the stop 74 also moves to the right and the rod control spring 78 begins to extend the rod 70, relieving the forward pressure of the rod on the valve means, whereupon the valves continue to open until they ultimately are fully opened and movement of the piston rod 16 to the right may be achieved at its normal rate.

As long asthe position of the piston rod stop 74 on the piston 18 is retained, the action described above will be repeated on each retraction stroke ofthe cylinderpiston assembly. The length of the retraction stroke can, of course, be changed by altering the position of the stop 74 axially of the rod 18, causing the stop 74 to later, as desired.

v they In any event, the mechanism 28 operates to establish a preliminary stopped position of the piston rod 16 at the end vof its predetermined stroke, with provision for overtravel beyond that position by an amount determined by the time it takes the valves 58 and 36 to attain their fully seated positions. In other words, the mechanism is effective to move the valve 36 rst to throttle the passage 24--14 and then to move the valve 58 to completely block the passage. To this extent, the mechanism gives substantially the same results as in the above-identified patent to Fletcher 2,615,430, with the signicant exception that overtravel may occur at the same speed as the original retraction stroke, since in the present design disconnection of the drive means 86-100 permits the large valve 36 to become unseated, thereby removing vthe restriction 54--56 from the passage. This result is achieved here by divorcing the valve 36 from the control rod 70 except through the connection 84. Stated otherwise, once the connection 84 is disconnected at 86--100, the valve 36 is independent of the position of the control rod 70, whereas in the Fletcher patent disconnection is not available.

Operaon-Overtravel cancelled -Despite the advantages of the provision for stop and overtravel, as described above, there are, as already indicated, instances in which it is desired to cancel or lockout the overtravel feature. For example, even in those systems in which the control valve is automatically returned to neutral in response to abnormal rise in pressure in the system, the operator may inadvertently hold the main control lever in its operating position and will automatically incur overtravel even though he does not desire it. ln some control systems in w-hich no provision is made for automatically returning the control valve to neutral, the system will automatically overtravel beyond the desired position. For the foregoing and other reasons, it is desirable that means such as the selector means 104 be provided.

' ln the foregoing stop and overtravel, ln the present phase description of the operation involving the selector means was retracted. of operation the selector means is extended (Fig. 3). The ibasic function of the selector means in the Fig. 3 position is to set a new position for the control rod 70. Since the rod 70 is connected by the lost-motion connection 84 to the inner valve 58, the selector means also affords a new position for that valve. This new position is materially short of its normal rear position as attainablein Fig. 1, for example. Stated otherwise, and referring now to Fig. l, it will be seen that the required distance of travel of the valve 36 before it seats is considerably shorter than that required to attain seating of the valve 58 at 62-64. Hence, the two valves are moved sequentially; that is, although start out at the same time and move in unison, the connection at 86-100 becomes disconnected when the valve 36 becomes seated and consequently the inner valve 58 is permitted to overtravel relative to the seated outer valve. To convert the system to operate without provision for overtravel is tantamount to cutting down the distance that the valve 58 has to travel, plus disconnection of the drive means 86-100, which automatically results from stopping the valve 58 in a new rear position forwardly of its normal rear position. This will be readily evident by comparing the positions of the valves 58 in Figs. l and 3, wherein it will be seen that in both gures the outer valve 36 is stopped rearwardly against the washer 42, but in Fig. l the connection 86--100 is effected whereas in Fig. 3 the sarne connection is released. Anothercomparison may be made on the basis of the axial distance between the head 62 of the valve 58 and the seat 64 of the valve 36 in the two figures, noting particularly in Fig. 3 that the head 62 and the seat 64 are practically in engagement.

the presently described- For purposes of clarity and exposition, the starting position ofthe piston 16 is the same as that in Fig. 1, but the position of the stop 74 on the piston rod has been changed so that thestop 74`occupies the same position in Fig. 3, relative tothe lug 72, that it does in Fig. l. In short, the stop 74 has been advanced on the piston rod by an amount equa-l to the distance between the fully-rear lug 72 in Fig. 1 and the stopped-short lug 72 in Fig. 3. In this circumstance, the final stop on the leftward stroke of the piston 16 in Fig. 4 will correspond to the position of the piston in Fig. 2. However, whereas in Fig. 2 the piston can have overtravel to the left, because the valve 58 has not seated, such overtravel is not available in Fig. 4, because the valve 58 has seated. if it is desired that the final position of the piston, with the selector means setting of Figs. 3 and 4,` coincide with the dotted-line position of the piston in Fig. 2, the stop '74 could retain the setting of Fig. 1 on the piston rod. O f course, other stopped positions of the piston are available according to the setting ofthe stop 74. However, as illustrative of the duality of the system, only the one position achieved as in Fig. 4 will be described. That is, the final position of the piston 16 in Fig. 4 corresponds to the first stopped (full-line) position of the piston 16 by seating of the valve 36 at 34 (Fig. 2). Stated otherwise, with the selector s'et as in Figs. 3 and 4, the piston 16 moves directly to only one position without being first stopped and then r'e-started.y

As previously indicated, when the selector means is eX- tended (Figs. 3 and 4) the control rod 70 is compelled to to occupy a new rear position and this is likewise true as to the valve 58, hence preventing connection of the drive means 86-109 after the drive means is initially and deliberately disconnected. In the present disclosure, the necessary disconnection may be effected by first manually pushing in on the control rod 7d until both valves 36 and 58 are seated. This will, of course, disconnect the connection at 86-106 and, before the control rod 7? is allowed to return, the set screw 1.06 is turned in and locked by the lock nut 108 to intercept the control rod 70 by engagement of the inner end of the set screw with the control rod lug 72. This sets the mechanism in the position of Fig. 3, with the seat 62 o-n the inner valve 58 just slightly behind the inner seat 6d on the outer valve 36. Accordingly, when the co-ntrol rod lug 72 is engaged by the piston rod stop 74, the inner valve 58 is advanced but slightly until it seats at 62-6-1, thereupon picking up the outer valve 36 so that further advance incurs advance of the two valves in unison and effects a blockade of the passage 24-14 without the intervening effect of the orifice means Sit-56.

When it is desired to extend the cylinder, the fluid entering via the inlet 14 can enter through the port or orifice 54 to back up the valve 58 against its spring 94 so as to establish communication between the `orifice 56 and the passage 24, whereupon the piston 16 is capable of moving to the right as described above, ultimately relieving the valve mechanism of the forward force of the control rod so that full-speed extension of the cylinder piston assembly is available.

To restore the mechanism to the condition of Fig. 1, it is necessary only to retract the set screw 106 clear of the control rod lug 72.

Summary As indicated, the present disclosure isbased upon a preferred embodiment of the invention and obviously contains features peculiar to that embodiment. However, the broad principles disclosed will readily suggest other constructions for attaining the same and additional objects, all of which will readily occur to those skilled in the art without departure from the spirit and scope of the invention.

What is claiid'isf k 1. In a Huid-pressure control system having a duidreceivable chamber, a passage for the liow of fluid to and from the chamber, and a part movable backand forth in the chamber, the improvement comprising; means affording a valve bore having a forward end leading to the passage; a normally rearwardly positioned first valve advanceable in the bore through a certain distance to a stopped forward position throttling Athe passage; a normally rearwardly positioned second valve advanceable in the bore through a normally greater distance to a forward position blocking the passage; a control member a'dvanceable from a stopped rear position and having one-way means engageable by the aforesaid part for advancement of said member by said part; first drive means interconnecting the control member and second valve for advance and return thereof in unison; first biasing means lfor returning the control member and second valve to their respective rearward positions; second drive means releasably interconnecting the rearwardly positioned valves in the aforesaid spaced relation and operative upon initial advance of the second valve and control member to advance the first valve to its forward position and thereupon releasable toenable further advance of the second valve by the `control member to its forward position, said second drive means being reconnectible between the valves upon return of the valves and control member to their respective rearward positions; second biasing means acting on the first valve to return said first valve to its rearward position for conditioning said second drive means for reconnection to the rearwardly positioned second valve; and stop means selectively operative on the control member for limiting rearward return thereof to a position short of its stopped rear position and thereby to hold the second valve in a position intermediate its forward and rearward positions whereby to reduce'the distance between said `second valve and its forward position and also to preclude reconnection of said second drive means so that the first valve can be moved rearwardly by its biasing means. y Y

2. The invention defined in claim l, in which: the first and second drive means are combined and comprise a `de'ten't maintaining a drive connection between the control member and second valve and biased into engagcment with the first valve for yielding to a disconnected position when the first valve advances to its Stopped forward position.

3. In a duid-pressure control system having a fluidreceivable chamber, a passage for the fiow of fiuid to and: from the chamber, and a part movable back and forth in the chamber, the improvement comprising: means affording a valve bore having a forward end leading to the passage; a normally rearwardly positioned first valve advance-able in the bore through a certain distance to a stopped forward position throttling the passage; a normally rearwardly positioned second valve advanceable in the bore through `a normally greater distancepto a forward position blocking the passage, said second valve including a control portion movable with said second valve as an indication of the position thereof, said control portion having one-way means engageable by the aforesaid part for advancement of said portion and second valve; first biasing means for returning the second valve and control portion rearwardly to the aforesaid rearward position of said second valve; drive means releasably interconnecting the rearwardly positioned valves in the aforesaid spaced relation and operative upon initial advance of the second valve and control portion to advance the first valve to its forward position and thereupon releasable to enable further advance of the second valve to its'forward position, said drive means being reconnectible between the valves upon return of the valves to their respective rearward positions; second biasing means acting on the first valve to return 9 said trst valve to its rearward position for conditioning said drive means for reconnection to the rearwardly positioned second valve; .and stop means selectively operative on the second valve for limiting rearward return thereof to a position lshort of its aforesaid rear position whereby to reduce the distance between said second valve-and its forward position and also to preclude reconnection of said drive means so that the irst valve can be moved rearwardly by its biasing means.

4. In a fluid-pressure control system having a iluidreceivable chamber, a passage for the flow of iiuid to and from the chamber, and a part movable back` and forth in the chamber, the improvement comprising: means affording a valve bore having a forward end leading to the passage land providing a passage-control seat; a tirst valve in the bore and having a front head seatable on said seat and having oriiice means therein operative when said valve isseated to enable reduced uid ow through the passage and said yvalve having a rear seat at which said orifice means opens; first means biasing the valve to a rearwardly stopped position spacing said head rearwardly of the passagecontrol seat; a coaxial second valve norm-ally spaced rearwardly of and adapted to seat on said rear seat to block the orice means; second means biasing the second valve to a normal rearwardly stopped position spaced behind the rear seat; means for advancing the second valve; releasable drive means connected between the valves in their respective rearwardly stopped positions so that advance of the second valve incurs advance of the irst valve until the latter seats, said drive means being thereupon releasable to enable further advance of the second valve until it seats on the rear seat, said iirst and second biasing means being loaded by said advance to return the valves independently to their respective rearwardly stopped positions to incur reconnection of the drive means; and means for selectively intercepting return of the second valve to stop said second valve at a new position intermediate its seated and normal rearwardly stopped positions to thereby reduce the distance between said second valve and the rear seat on the rearwardly positioned iirst valve and also to prevent reconnection of the drive means so that subsequent advance of the second valve from its new position iirst seatsv said second valve on the tirst valve rear seat and then advance both valves in unison to seat the first valve.

5. In a huid-pressure control system having auidreceivable chamber, a passage for the flow of iiuid to and from the chamber, and a part movable back and forth in the chamber, the improvement comprising: means affording a valve bore having a forward end leading to the `passage and providing a passage-control seat; a first valve in the bore and having a front head seatable on said seat andv having oriiice means therein operative when said valve is seated to enable reduced iiuid -iiow through the passage and said valve having a rear seat at which said orifice means opens; iirst means biasing the valve to a rearwardly stopped position spacing said head rearwardly of the passage-control seat; a coaxial second valve normally spaced rearwardly of and adapted to seat on said rear seat to block the orifice means; a control member advanceable from a normal rearwardly stopped position for advancing the valves; a fore-and-aft lost-motion connection between the member and second valve normally biased to extend the second valve forwardly relative to the member and yieldable to enable limited forward overrun of said second valve by said member; second means biasing the control member to its normal rearwardly stopped position arid operative via said lost-motion connection to retract the second valve to a rearward position spaced behind the rear seat on the iirst valve; drive means effectuated by the normally biased lostmotion connection to interconnect the two valves in their respective rearward positions so that advance of the control member incurs -advance of the valves in unison aiseeos until the iirst valve seats to temporarily'x stop both valves;

said lost-motion connection enabling thereupon yielding and forward overrun by the control member to disconl nect the drive means for advance of the second valve untill it seats; and means for selectively intercepting return of the second' valve to hold said second valve in a new positionshort of its former rear position to thereby reduce the distance between said second valve and the rear seat on the rearwardly positioned first valve and also to pre# vent reconnection of the drive means so that subsequent advance of the second valve from its new position tirs-t seats said second valve on the irst valve rear seat and then advance both Valves in unison to seat the iirst valve.

6. The invention deiined in claim 5, in which: the first valve has a tubular rear part including an internal rearwardly facing abutment; the second valve is carried within said part and itself has a tubular rear part provided with a radial aperture in substantial radial register with said abutment when both valves are in their respective normal rearwardly stopped position; the drive means includes the aperture, the abutment, a detent retained in the aperture and engaging the control member, said detent being urged outwardly to engage the abutment and retaining engagement with the control member upon biased extension of the lost-motion means and said `detent being radially retractible from said abutment upon yielding of said lost-motion means.

7. The invention dened in claim 6, in which: the detent also achieves part of the lost-motion connection, said control member having .a recess therein defined by front and rear spaced apart stop portions against the rear one of which theidetent is normally urged by the lostmotion connection bias, said recess having a front cam surface adapted to hold the detent normally outwardly into engagement with the abutment and a rear cam surface enabling retraction of the detent upon yielding of the lostmotion connection.

8. In a Huid-pressure control system having a iiuidreceivable chamber, a passage for the iiow of iiuid to and from the chamber, and a part movable back and forth in the chamber, the improvement comprising: valve means for controlling fluid iiow through the passage, including a iirst valve member biased to an open position and movable to a passage-blocking position, said valve member having means affording a restrictive port operative in said passage-blocking position to enable reduced fluid flow through the passage, said valve means further including a second valve member movable relative to the first valve member from a first position clear of the restrictive port to a position blocking the port; drive means releasably interconnecting the two valve members while in their respective open and clear positions for movement in unison to first seat the first valve member, said drive means being releasable in response to seating of the first valve member to enable relative movement of the second valve member to its port-blocking position; means for positively releasing the drive means preliminarily to seating of the first valve member toenable the second valve member to be moved to its port-blocking position; additional means engageable between the valve members when the second valve member is thus moved preliminarily to its port-blocking position to incur movement of said members in unison to the passage-blocking position of the first valve member; and control means engageable by and movable with the aforesaid part and operative through the drive means when connected and through the second valve member and said additional means when the drive means is positively released, for moving the valve members as aforesaid.

9. In a fluid-pressure control system having a uidreceivable chamber, a passage for the tiow of fluid to and from the chamber, and a part movable back and forth in the chamber, the improvement comprising: valve means for controlling tiuid ow through the passage, including a tirst valve member biased to an open position and'fmovable to a passage-blocking position, said valve member having means affording a restrictive port operative in said passage-blocking position to enable reduced fluid fiow through the passage, said valve means further including a second valve member movable relative to the first valve member from a first position clear of the restrictive port to a position blocking the port; control means engageable by and movable with the aforesaid part for incurring sequential movement of the valve members to move the first valve member to its passageblocking position and then to move the second valve member to its port-blocking position; and selector means operative independently of said port to releasably retain the second valve member in its port-blocking position.

10. In a fluid-pressure control system having a fluidreceivable chamber, a passage for the flow of fiuid to and from the chamber, and a part movable back and forth in the chamber, the improvement comprising: means affording a valve bore having a forward end leading to the passage; a normally rearwardly positioned first valve advanceable in the bore through a certain distance to a stopped forward position throttling the passage; a normally rearwardly positioned second valve advanceable in the bore through a normally greater distance to a forward position blocking the passage; a control member advanceable from a stopped rear position and having one-way means engageable by the aforesaid part for advancement of said member by said part; first drive means interconnecting the control member and second valve for advance and return thereof in unison; first biasing. means for returning the control member and second valve to their respective rearward positions; second drive means releasably interconnecting the rearwardly positioned valves in the aforesaid spaced relation and operative upon initial advance of the second valve and control member to advance the first valve to its passagethrottling position and thereupon releasable to enable fur- .t'heradvance of the second valve by the control member to its forward position; and second biasing means acting on the first valve to return said first valve toward -its rearward position upon release of said second drive means whereby to remove said first valve from its passage-throttling position.

ll. Ina fiuid-pressure control system having a fiuidreceivable chamber, a passage for the flow of fluid to and from the chamber, and a part movable back and forth vin the chamber, the improvement comprising: means affording a valve bore having a forward end ,leading to the passage; a normally rearwardly positioned first valve advanceable in the bore through a certain distance to a stopped forward position controlling the passage; a normally rearwardly positioned second valve advanceable in the bore through a normally greater distance to a forward position controlling the passage; means for advancing the second valve to its forward position; first biasing means for returning the second Valve to its rearward position; drive means releasably interconnecting the rearwardly positioned valves in the aforesaid spaced relation and operative upon initial advance of the second valve to advance the first valve to its forward position retard movement of said `leasable upon further shifting of the second valve lbeyond 12 and thereupon releasable to enable further advance of the second valve to its forward position; second biasing means acting on the first valve to return said first valve toward its rearward position upon release of said drive means whereby to remove said first valve temporarily from its forward position; and means engageable between the valves whereby the second valve, upon said further advance of said second valve to its forward position, nicks up the first valve and again advances said first valve to its forward position.

l2. In a fluid-pressure control system having a fiuidreceivable chamber, a passage for the flow of fiuid to and from the chamber, and a part movable back and forth in the chamber, the improvement comprising: means affording a valve bore having `a forward end leading to the passage; normally rearward positioned first valve advanceable in the bore through a certain distance to a stopped forward position controlling the passage; a normally rearwardly positioned second -valve advanceable in the bore through a normally greater distance to a forward position controlling the passage; means for advancing the second valve to its forward position; first biasing means for returning the second valve to its rearward position; drive means releasably interconnecting the rearwardly positioned valves in the aforesaid spaced relation and operative upon initial advance of the second valve to advance the first valve to its forward position and thereupon releasable to enable further advance of the second valve to its forward position; and second biasing means acting on the first valve to return said first valve toward its rearward position upon release of said drive means whereby to remove said first valve from its forward position 13. `In a Afiuid-pressure control system having a fiuidreceivable chamber, a passage connected to the chamber, and a part movable in the chamber according to the flow rate through the passage, the improvement comprising: a first valve normally biased to an open position and shiftable to a passage-restricting position; a second normally open valve shiftableto a passage-closing position; means operated by said part for moving the second valve to its passage-closing position; and releasable drive means engaged between the valves for incurring shifting of the first valve to its passage-restricting position upon shifting of the second valve to an intermediate position toward but short of its passage-closing position so as to part, said drive means being resaid intermediate position to enable biased return of the first valve to its open position while the second valve -is still short of its passage-closing position so that further movement of said part is free of said retarding effect and incurs shifting of the second valve to its passage-closing position without the passage-restricting effect of the first valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,615,430 Fletcher Oct. 28, 19152 

